Therapy for pneumococcal infection at the millennium: doubts and certainties

ALK-JNK signaling promotes NLRP3 inflammasome activation and pyroptosis via NEK7 during Streptococcus pneumoniae infection

Streptococcus pneumoniae (S. pneumoniae), a clinically important pathogen worldwide, causes serious invasive diseases, such as pneumonia, otitis media, and meningitis. The NLR family pyrin domain-containing 3 (NLRP3) inflammasome, an important component of the innate immune system, plays a key role in defense against pathogen infection; however the specific activation mechanism induced by S. pneumoniae infection is not fully understood. Here, primary mouse macrophages were selected as the in vitro cell model, and the effect of kinases on S. pneumoniae infection-induced NLRP3 inflammasome activation was investigated in vivo and in vitro using the western blot/RT-PCR/Co-IP/immunofluorescence staining/ELISA with or without kinase inhibitor or siRNA pretreatment. In this study, we found that the formation of the NEK7-NLRP3 complex significantly increased during S. pneumoniae infection and that anaplastic lymphoma kinase (ALK) and Jun N-terminal kinase (JNK) were phosphorylated rapidly. ALK and JNK inhibitors significantly reduced the ability of bacterial killing, the gene expression of NLRP3 inflammasome, the formation of apoptosis-associated speck-like protein containing caspase-recruitment domain (ASC) specks and the NEK7-NLRP3 complex, which in turn decreased the activation level of NLRP3 inflammasome-associated molecules and the maturation of interleukin-1β (IL-1β). In addition, ALK regulated the phosphorylation of JNK. Interestingly, the ALK/JNK/NEK7-NLRP3 signaling pathway is also involved in regulating pyroptosis and IL-1β secretion triggered by S. pneumoniae infection. In conclusion, our data suggest, for the first time, that the ALK/JNK/NEK7-NLRP3 signaling pathway may play an important role in NLRP3 inflammasome activation and pyroptosis and consequently regulate the host immune response upon S. pneumoniae infection.

Predominance of Serogroup 19 CC320/271 among Penicillin-Nonsusceptible Streptococcus pneumoniae Isolates after Introduction of the PCV7 Vaccine in Several Regions of Japan

Multidrug-resistant Streptococcus pneumoniae serogroup 19, including serotypes 19A and 19F, associated with clonal complex 320/271 (CC320/271), has been previously shown to be predominant in many countries after introduction of a 7-valent pneumococcal conjugate vaccine (PCV7). However, in Japan there has been no epidemiological research focused on penicillin-nonsusceptible isolates after this event. Therefore, we aimed to characterize penicillin-nonsusceptible S. pneumoniae (PNSSP; penicillin minimum inhibitory concentration [MIC] ≥ 4.0 μg/ml) after the introduction of PCV7 in Japan. Throughout Japan, we collected 1,057 pneumococcal isolates from 2010 to 2014. We then evaluated MICs and performed serotyping, multilocus sequence typing, and sequencing of penicillin-binding protein genes in 51 isolates (penicillin MIC ≥ 2.0 μg/ml). Twenty-three isolates (2.2%) showed penicillin nonsusceptibility (penicillin MIC ≥ 4.0 μg/ml). Serotypes 19F (14 isolates, 60.9%) and 23F (4 isolates, 17.4%), which are covered by the vaccine, were predominant among PNSSP strains. Only 3 isolates belonged to nonvaccine serotype 19A. Among the PNSSP isolates, CC320/271 (16/23 strains, 69.6%) was the most prevalent clone. Moreover, CC320/271 clones showed high MIC values of a third-generation cephalosporin. Thus, we demonstrated clonal predominance of serogroup 19 CC320/271 with strong resistance to β-lactams including a third-generation cephalosporin among PNSSP isolates.

A model assessment of the importance of direct photolysis in the photo-fate of cephalosporins in surface waters: Possible formation of toxic intermediates

The direct and indirect photodegradation of six cephalosporins was predicted using a photochemical model, on the basis of literature values of photochemical reactivity. Environmental photodegradation would be important in surface water bodies with depth ⩽ 2-3m, and/or in deeper waters with low values of the dissolved organic carbon (DOC ⩽ 1 mg C L(-1)). The half-life times would range from a few days to a couple of weeks in summertime. In deeper and higher-DOC waters and/or in different seasons, hydrolysis could prevail over photodegradation. The direct photolysis of cephalosporins is environmentally concerning because it is known to produce toxic intermediates. It would be a major pathway for cefazolin, an important one for amoxicillin and cefotaxime and, at pH<6.5, for cefapirin as well. In contrast, direct photolysis would be negligible for cefradine and cefalexin. The DOC values would influence the fraction of photodegradation accounted for by direct photolysis in shallow water, to a different extent depending on the role of sensitisation by the triplet states of chromophoric dissolved organic matter.

Antimicrobial resistance among invasive isolates of Streptococcus pneumoniae collected across Canada

Between 2002 and 2003, 736 nonduplicate Streptococcus pneumoniae isolated from blood cultures were collected from 7 of 10 Canadian provinces (10 tertiary care centers). Microdilution broth susceptibility testing was performed using the method prescribed by the Clinical Laboratory Standards Institute. Of the isolates, 16.85% were nonsusceptible to penicillin and 5.4% were highly resistant. Of the S.pneumoniae, 14.1% had reduced susceptibility to erythromycin and 47% had been accounted for by the M phenotype. No isolates were recovered that were resistant to telithromycin. Only 6 isolates were resistant to levofloxacin and gatifloxacin. Of these, 5 strains had intermediate susceptibility to moxifloxacin and 1 was considered susceptible. The rates observed in this study are in keeping with previous surveillance studies among noninvasive isolates.

Resistance patterns of selected respiratory tract pathogens in Poland

This study presents the results of a survey of the in-vitro susceptibility to antimicrobial agents of major pathogens responsible for community-acquired respiratory tract infections in Poland during 2002-2004. The collection of 1184 bacterial isolates comprised 398 Streptococcus pneumoniae, 344 Haemophilus influenzae, 302 Streptococcus pyogenes and 140 Moraxella catarrhalis. Among the pneumococcal isolates, 16.8% were penicillin-non-susceptible (PNSP), of which 80.6% were identified as multidrug-resistant. Overall, 9.0% of H. influenzae isolates were beta-lactamase-positive, although this percentage increased noticeably in the third year of the study. Based on PCR results, 12.8% of H. influenzae isolates were identified as low-level beta-lactamase-negative, ampicillin-resistant (BLNAR), and one isolate as low-level beta-lactamase-positive, amoxycillin-clavulanic acid-resistant (BLPACR). Pulsed-field gel electrophoresis (PFGE) classified 45 H. influenzae isolates with altered penicillin-binding proteins into 15 PFGE types, including two predominant types (with four and six sub-types) containing 15 and ten isolates, respectively. Resistance to tetracycline, erythromycin and clindamycin was found in 20.9%, 8.9% and 4.6% of S. pyogenes isolates, respectively. The production of beta-lactamase characterised 91.4% of M. catarrhalis isolates. In summary, the overall occurrence of PNSP in Poland remains stable, although there was a noticeable increase in the proportion of fully-resistant isolates. A rising trend in the prevalence of beta-lactamase producers and low-level BLNAR isolates was observed among Polish isolates of H. influenzae.

Telithromycin in the treatment of pneumococcal community-acquired respiratory tract infections: a review

OBJECTIVES

A pooled analysis of 14 Phase III studies was performed to establish the clinical and bacteriologic efficacy of telithromycin 800 mg once daily in the treatment of pneumococcal community-acquired respiratory tract infections (RTIs).

METHODS

Data were examined from 5534 adult/adolescent patients with community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), or acute bacterial sinusitis, who had received telithromycin for 5-10 days or a comparator antibacterial.

RESULTS

Streptococcus pneumoniae was identified in 704/2060 (34.2%) bacteriologically evaluable patients. The respective per-protocol clinical cure rates for telithromycin and comparators were 94.3% and 90.0% (CAP); 81.5% and 78.9% (AECB); 90.1% and 87.5% (acute sinusitis); 92.7% and 87.6% (all indications). Clinical cure rates were 28/34 (82.4%) and 5/7, respectively, for penicillin-resistant infections, and 44/52 (84.6%) and 11/14, respectively, for erythromycin-resistant infections. Of 82 patients with pneumococcal bacteremia, 74 (90.2%) were clinically cured after telithromycin treatment, including 5/7 and 8/10 with penicillin- or erythromycin-resistant strains, respectively. Adverse events considered possibly related to study medication were reported by 1071/4045 (26.5%) telithromycin and 505/1715 (29.4%) comparator recipients. These events were generally of mild/moderate severity, and mainly gastrointestinal in nature.

CONCLUSIONS

As S. pneumoniae is the leading bacterial cause of community-acquired RTIs, and antibacterial resistance is increasing among this species, these findings support the use of telithromycin as first-line therapy in this setting.

Pharmacodynamic evaluation of tosufloxacin against Streptococcus pneumoniae in an in vitro model simulating serum concentration

We compared the antibacterial effects and the emergence of resistance to tosufloxacin or levofloxacin for Streptococcus pneumoniae by simulating the serum concentration according to the Japanese clinical regimens using an in vitro pharmacokinetic-pharmacodynamic model. For quinolone-susceptible strain ATCC49619, tosufloxacin showed bactericidal activity, given that both the AUC(0-24h)/MIC ratios at the dosage of 150 mg t.i.d. and 300 mg b.i.d. of tosufloxacin tosilate were 138 and 193, and the C(max)/MIC ranges were 7.93-10.2 and 15.9-17.6, respectively, which were greater than those of levofloxacin (100 mg t.i.d. and 200 mg b.i.d.). The greater area above the killing curves (AAKCs) or shorter time to achieve 99.9% killing (99.9% KT) in both models of tosufloxacin than those of levofloxacin was related to their larger AUC(0-24h)/MIC and C(max)/MIC. Exposure of only 100 mg t.i.d. of levofloxacin led to outgrowth of the parC mutants, which were twofold less susceptible to levofloxacin than the parent strain. Neither of the tosufloxacin tosilate regimens resulted in isolation of resistant mutants of this strain. For the parC mutant strain D-3197, both the AUC(0-24h)/MIC and C(max)/MIC ratios of tosufloxacin were greater than those of levofloxacin, which resulted in comparable or better bactericidal activity as compared to those of levofloxacin. However, both fluoroquinolones and both regimens led to outgrowth of resistant mutants, which possessed a mutation in gyrA in addition to parC. In conclusion, tosufloxacin is superior to levofloxacin in bactericidal activity against S. pneumoniae in the Japanese clinical regimens, especially in the quinolone-susceptible strain, without emergence of resistant subpopulations.

Mutant prevention concentrations for single-step fluoroquinolone-resistant mutants of wild-type, efflux-positive, or ParC or GyrA mutation-containing Streptococcus pneumoniae isolates

Three fluoroquinolone-susceptible and five fluoroquinolone-resistant (two with ParC Ser79Phe mutations, one with a GyrA Ser81Phe mutation, and two that were efflux positive) Streptococcus pneumoniae isolates were exposed to one, two, four, eight, and sixteen times the MICs of ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin. Mutational frequencies were calculated at each multiple of the MIC for which growth was observed. Mutant prevention concentrations (MPCs) and the multiple of the MIC at the MPC (MP(MIC)) were evaluated. All resulting mutants were sequenced for quinolone resistance-determining region changes in GyrA and ParC and were evaluated for reserpine-sensitive efflux. The MPC order was generally ciprofloxacin > levofloxacin > gatifloxacin > moxifloxacin > gemifloxacin. The MP(MIC) order varied depending on the genetic constitution of the original isolates from which the mutants were generated. For those mutants created from fluoroquinolone-susceptible isolates (those that had wild-type ParC and GyrA and were efflux negative), the MP(MIC) order was ciprofloxacin = moxifloxacin > gemifloxacin > levofloxacin > gatifloxacin. The MP(MIC)s of each fluoroquinolone for mutants created from isolates with a ParC mutation (with wild-type GyrA and efflux negative) were similar. A similar occurrence was observed with the mutants created from the efflux-positive isolates (with wild-type ParC and GyrA). The MP(MIC) order for the mutants created from the isolate with a GyrA mutation (with wild-type ParC and efflux negative) was ciprofloxacin = gemifloxacin > levofloxacin = moxifloxacin > gatifloxacin. Gatifloxacin, levofloxacin, and moxifloxacin may be intrinsically more able to prevent the development of resistance by fluoroquinolone-susceptible isolates, isolates that are efflux positive, or isolates that carry a GyrA mutation. However, once a ParC mutation is present, the MPC increases dramatically for all fluoroquinolones.

Septic arthritis in the adult caused by Streptococcus pneumoniae: A report of 4 cases and review of the literature

OBJECTIVES

To identify coexistent diseases, clinical features, approaches to management, and predictors of outcome in patients with pneumococcal septic arthritis.

METHODS

Case series of 4 adults with Streptococcus pneumoniae septic arthritis seen at a university hospital, plus a review of 115 adults with pneumococcal septic arthritis reported in the medical literature from 1973 through 2003.

RESULTS

Among our 4 patients, 3 had polyarticular infections, joint prostheses were involved in 1, 3 had underlying joint diseases, and 1 had concurrent meningitis. Infection was caused by penicillin-intermediate/cephalosporine-susceptible S pneumoniae in 1 patient and penicillin-resistant/cephalosporine-intermediate S. pneumoniae in 1 patient. After a mean treatment duration of 6 weeks, all patients were clinically cured of infection. Review of the literature identified 115 cases of S pneumoniae septic arthritis in adults. Clinical data were available for 107 patients. Twenty-nine cases were polyarticular (26%), joint prostheses were involved in 15 patients (13%), and 61 patients had underlying joint disease (57%). Meningitis was a concurrent infection in 15 cases. The presumed primary focus of infection was the respiratory tree in 44 patients. Ninety-six percent of cases were caused by penicillin-susceptible organisms. Cure of infection with survival was achieved in 83% (79 of 95) of patients with native joint septic arthritis and in 67% (8 of 12) of patients with prosthetic joint infection. A good functional outcome (full range of motion or return to baseline range of motion) after infection was achieved by 44 of 71 patients (62%) with native joint infection and by 4 of 7 patients (57%) with infections of prosthetic joints. The likelihood of cure of infection or good functional outcome was not influenced by method of joint drainage.

CONCLUSIONS

S pneumoniae is an uncommon, but not rare, cause of septic arthritis in the adult. Many patients have underlying joint disease (especially rheumatoid arthritis) and coexistent alcoholism. Although most infections involve native joints, prosthetic joint infections comprise 13% of cases. Polyarticular disease occurs in approximately one quarter of patients. Most patients have a preceding or concurrent extra-articular focus of pneumococcal infection. To date, the majority of reported infections are caused by penicillin-susceptible organisms, so penicillin G or a third-generation cephalosporine such as ceftriaxone remains the appropriate treatment option. However, infection with drug-resistant organisms is likely to be an increasing problem in the future. With directed antimicrobial therapy and appropriate joint drainage, the outcome is generally good for patients with native joint infections. In contrast, only two thirds of patients with infections of prosthetic joints survive their infections. Approximately 40% of surviving patients experience functional impairment or chronic pain as a sequelae of their infection.

Antimicrobial susceptibility to levofloxacin and other antibacterial agents among common respiratory pathogens—a Brazilian perspective from the GLOBAL Surveillance Initiative 2001–2002

The GLOBAL (Global Landscape On Bactericidal Activity of Levofloxacin) Surveillance programme monitored antimicrobial susceptibility patterns of the key respiratory tract pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis collected in Brazil during 1997-1998, 1999-2000 and 2001-2002. Penicillin and azithromycin resistance among S. pneumoniae strains increased from 1997-1998, reaching 7.9% and 9.5%, respectively, in 2001-2002. Although decreasing by 4.9% since the previous study, trimethoprim-sulphamethoxazole resistance remained high at 33.7%. Concurrent resistance to penicillin, azithromycin and trimethoprim-sulphamethoxazole was seen in 2.9% of the S. pneumoniae isolates collected. Levofloxacin remained extremely active against S. pneumoniae, with 0.3% resistance reported in 1997-1998 and 0% resistance in 1999-2000 and 2001-2002. beta-Lactamase production in H. influenzae was > 10% in all three studies, with correspondingly high rates of ampicillin resistance. Trimethoprim-sulphamethoxazole was the least active agent tested against H. influenzae, with resistance rates of > 40% recorded in all three studies. All H. influenzae isolates were susceptible to cefuroxime, ceftriaxone, azithromycin and levofloxacin. Of the M. catarrhalis isolates, 98.0% in 1997-1998, 98.0% in 1999-2000 and 81.8% in 2001-2002 were beta-lactamase-positive. The continued high prevalence of antimicrobial resistance in Brazil underscores the importance of current surveillance initiatives. Levofloxacin, a fluoroquinolone prescribed widely for respiratory tract infections, continued to show potent activity against key respiratory pathogens.

Prevention and management of antibacterial resistance for primary care patients with respiratory tract infections

This review examines the problem of increasing antibacterial resistance among the pathogens commonly associated with community-acquired respiratory tract infections, particularly Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The increases in morbidity, mortality, and treatment cost associated with increased resistance to available antibiotics are challenging prescribers to find more effective therapeutic strategies. A MEDLINE search of the literature from 1966 to the present was performed to seek data relevant to the issue of resistance, especially the negative effects on patient outcomes and costs of therapy. Several observations and conclusions emerged. Data are lacking on local resistance patterns, broad-spectrum agents are overprescribed when narrower-spectrum choices would be more appropriate, a need exists for educational programs to encourage restricting drug use and changing prescribing habits, and there is a need for new antibiotic choices. The best antibiotic options are agents with a tailored spectrum of activity that are targeted at particular respiratory tract pathogens and have low potential to select for resistant organisms.

Antimicrobial Resistance among Isolates of Respiratory Tract Infection Pathogens from the Southern United States: Data from the PROTEKT US Surveillance Program 2000/2001

BACKGROUND

PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) was established in 2000 to monitor antimicrobial resistance among respiratory tract pathogens across the United States.

METHODS

During 2000 to 2001, 75 southern US centers collected 3,867 Streptococcus pneumoniae, 1,455 Streptococccus pyogenes and 1,042 Haemophilus influenzae.

RESULTS

Overall, 46.1% of S. pneumoniae isolates were nonsusceptible to penicillin, 35.8% were resistant to erythromycin, and 0.5% were resistant to fluoroquinolones. Against S. pneumoniae the most active agents were telithromycin (99.7% susceptible), linezolid (99.8%) and the fluoroquinolones (levofloxacin 99.4%, gatifloxacin 99.5%). The prevalence of erythromycin-resistant S. pyogenes isolates was 4.5%. Telithromycin, at concentration of < or = 1 mg/L, inhibited 99.9% of S. pyogenes. The prevalence of beta-lactamase positive H. influenzae was 26.2%. Telithromycin was active (MIC90 4 mg/L) against H. influenzae, irrespective of beta-lactamase production.

CONCLUSION

The prevalence of penicillin and macrolide resistance among respiratory tract pathogens from the southern United States is high. Fluoroquinolone resistance is low. Telithromycin is highly active against respiratory tract pathogens with reduced susceptibility to beta-lactams, macrolides, and fluoroquinolones.

Antimicrobial resistance in respiratory tract Streptococcus pneumoniae isolates: results of the Canadian Respiratory Organism Susceptibility Study, 1997 to 2002

A total of 6,991 unique patient isolates of Streptococcus pneumoniae were collected from October 1997 to June 2002 from 25 medical centers in 9 of the 10 Canadian provinces. Among these isolates, 20.2% were penicillin nonsusceptible, with 14.6% being penicillin intermediate (MIC, 0.12 to 1 microg/ml) and 5.6% being penicillin resistant (MIC, > or =2 microg/ml). The proportion of high-level penicillin-resistant S. pneumoniae isolates increased from 2.4 to 13.8% over the last 3 years of the study, and the proportion of multidrug-resistant S. pneumoniae isolates increased from 2.7 to 8.8% over the 5-year period. Resistant rates (intermediate and resistant) among non-beta-lactam agents were as follows: macrolides, 9.6 to 9.9%; clindamycin, 3.8%; doxycycline, 5.5%; chloramphenicol, 3.9%; and trimethoprim-sulfamethoxazole, 19.0%. Rates of resistance to non-beta-lactam agents were higher among penicillin-resistant strains than among penicillin-susceptible strains. No resistance to vancomycin or linezolid was observed; however, 0.1% intermediate resistance to quinupristin-dalfopristin was observed. The rate of macrolide resistance (intermediate and resistant) increased from 7.9 to 11.1% over the 5 years. For the fluoroquinolones, the order of activity based on the MICs at which 50% of isolates are inhibited (MIC(50)s) and the MIC(90)s was gemifloxacin > clinafloxacin > trovafloxacin > moxifloxacin > grepafloxacin > gatifloxacin > levofloxacin > ciprofloxacin. The investigational compounds ABT-773 (MIC(90), 0.008 microg/ml), ABT-492 (MIC(90), 0.015 microg/ml), GAR-936 (tigecycline; MIC(90), 0.06 microg/ml), and BMS284756 (garenoxacin; MIC(90), 0.06 micro g/ml) displayed excellent activities. Despite decreases in the rates of antibiotic consumption in Canada over the 5-year period, the rates of both high-level penicillin-resistant and multidrug-resistant S. pneumoniae isolates are increasing in Canada.

Telithromycin in the treatment of community-acquired pneumonia: a pooled analysis

The efficacy of telithromycin has been assessed in six Phase III studies involving adults with mild to moderate community-acquired pneumonia (CAP) with a degree of severity compatible with oral therapy. Patients received telithromycin 800 mg once daily for 7-10 days in three open-label studies (n=870) and three randomized, double-blind, comparator-controlled studies (n=503). Comparator antibacterials were amoxicillin 1000 mg three-times daily, clarithromycin 500 mg twice daily and trovafloxacin 200 mg once daily. Clinical and bacteriological outcomes were assessed 7-14 days post-therapy. Among telithromycin-treated patients, per-protocol clinical cure rates were 93.1 and 91.0% for the open-label and comparative studies, respectively. Telithromycin treatment was as effective as the comparator agents. High eradication and clinical cure rates were observed for infections caused by key pathogens: Streptococcus pneumoniae including isolates resistant to penicillin G and/or erythromycin A (95.4%), Haemophilus influenzae (89.5%) and Moraxella catarrhalis (90%). Telithromycin was also highly effective in patients with infections caused by atypical and/or intracellular pathogens and those at increased risk of morbidity. Telithromycin was generally well tolerated. Telithromycin 800 mg once daily for 7-10 days offers a convenient and well-tolerated first-line oral therapy for the empirical treatment of mild to moderate CAP.

Bacterial resistance--the clinical challenge

Resistance to antibacterial agents has increased among many species of bacterial pathogens in the last two decades. While this has been recognized and has been a matter of concern among those concerned with infectious diseases, it is only relatively recently that prescribing physicians have become aware of the problem. A range of official bodies, both national and international, have proposed a range of strategies for controlling this increase in resistance. The relationship between resistance and clinical efficacy or failure is unclear in many areas, although increasingly resistance can be seen to be associated with a less than optimal clinical response. Although the relationship between antibiotic use and resistance is complex, there is an assumption that excessive use of antibacterials may drive an increase in resistance. The term 'prudent prescribing' is frequently used in official documents, but it is not easy for the prescriber to determine exactly what is prudent prescribing. There have been efforts to reduce the unnecessary use of antibacterials in the treatment of many community respiratory infections where the etiological agent is likely to be viral. Guidelines for prescribing have been drawn up by governments and professional societies but their impact can be variable. They need to take account of the changing patterns of resistance, for example the rise in high-level penicillin resistance among pneumococci. They also need to be readily accessible to the practicing clinician. Surveillance systems are available in abundance and these may be local, national, or international. They often, however, suffer from drawbacks and are frequently selective. Frequently the prescriber does not have ready access to the most appropriate data. Integrated strategies to control resistance are urgently needed, as are improved rapid diagnostic facilities.

Prospective epidemiologic survey of patients with community-acquired pneumonia requiring hospitalization in Switzerland

BACKGROUND

Community-acquired pneumonia (CAP) is a common problem and the principal infection requiring hospitalization, but its treatment is complicated by the difficulty in microbiological diagnosis and the increasing incidence of antibiotic resistance among respiratory pathogens. The purpose of this paper is to present the main epidemiologic features of patients with CAP requiring hospitalization in our country.

METHODS

We enrolled three hundred and eighteen adult patients with CAP requiring hospitalization in seven large medical centers in Switzerland during two winter periods. The patients' mean age was 70.4 years. This study describes the epidemiology of these patients. Clinical, radiologic and microbiological evaluations were performed at study entry during treatment, and at 4 weeks post-therapy. For microbiological diagnostic purposes, sputum culture, throat swab culture, PCR, blood cultures, Legionella urinary antigen and serologic evaluations were also performed.

RESULTS

Despite the higher mean age, the overall mortality rate was 8%, lower than in other comparable studies. The most common underlying diseases present at study entry were cardiac failure (23%), chronic obstructive pulmonary disease (20%), renal failure (15%), and diabetes (12%); 40% of the patients were smokers. Although dyspnea, cough and positive pulmonary auscultation findings were present in about 90% of patients, fever >38 degrees C was present in only 64%. The most frequently isolated respiratory pathogens were Streptococcus pneumoniae (12.6%), Haemophilus influenzae (6%), Staphylococcus aureus (1.6%), and Moraxella catarrhalis (1.6%). Atypical pathogens were frequently found, with the following distribution: Mycoplasma pneumoniae, 7.5%; Chlamydia pneumoniae, 5.3%; and Legionella pneumophila, 4.4%. The mean duration between onset of symptoms and hospital admission was 4.8 days, and the mean treatment duration was 12.1 days. Two weeks after the start of therapy, although clinical symptoms were absent, radiologic infiltrates were still present in 24% of patients.

CONCLUSIONS

The microbiological diagnosis in CAP can be established in only about 50% of cases with the combination of several diagnostic tools. Epidemiologic surveys of CAP should be performed on a regular basis, regionally, as a way to improve the management of these infections.

Penicillin-binding protein 1A, 2B, and 2X alterations in Canadian isolates of penicillin-resistant Streptococcus pneumoniae

Alterations within the penicillin-binding domain of penicillin-binding protein (PBP) genes pbp1a, pbp2b, and pbp2x were determined for 15 Canadian isolates of Streptococcus pneumoniae. All penicillin-nonsusceptible S. pneumoniae isolates showed a variety of PBP 2X substitutions and contained a Thr445-Ala change after the PBP 2B SSN motif. Only isolates for which penicillin MICs were > or =0.5 micro g/ml had PBP 1A alterations near the STMK and SRN motifs. Sequence analysis revealed identical PBP 1A, PBP 2B, and PBP 2X substitution patterns among all isolates for which penicillin MICs were > or =1 micro g/ml.

Streptococcus pneumoniae as an agent of nosocomial infection: treatment in the era of penicillin-resistant strains

Streptococcus pneumoniae is a well-known agent of community-acquired infections such as sinusitis, otitis media, pneumonia, bacterial meningitis, bacteremia and acute exacerbations of chronic bronchitis. However, the role of S. pneumoniae as a cause of nosocomial infections of respiratory tract, bloodstream and central nervous system is more and more recognized, primarily in high-risk patients with depression of their immune function. Therapy of pneumococcal infections is made difficult by the emergence and spread of bacterial resistance to penicillin and other beta-lactams as well as to a number of antimicrobials such as macrolides, chloramphenicol, tetracyclines and sulfonamides. This epidemiological situation is a cause for concern world-wide, but it primarily affects some European countries, North America, South Africa and the Far East. The main consequence on therapeutic grounds is that in severe infections such as bacterial meningitis, the addition of vancomycin to a third-generation cephalosporin is advisable while awaiting laboratory test results, even in areas with low prevalence of penicillin-resistant pneumococci. However, a beta-lactam agent can also be a valid choice in the presence of potentially lethal infections such as pneumonia or in the case of penicillin intermediately resistant isolates. In recent years, new alternative molecules have been introduced into clinical practice for therapy of infections caused by penicillin-resistant pneumococci. In both in vivo and in vitro studies, drugs of the classes of fluoroquinolones (levofloxacin, moxifloxacin, gatifloxacin), streptogramins (quinupristin/dalfopristin) and oxazolidinones (linezolid) have shown good microbiologic and clinical efficacy against penicillin-resistant pneumococci. In this era of world-wide spread of penicillin-resistant pneumococci, use of polysaccaride or conjugated vaccines is highly recommended.

Linezolid: pharmacokinetic characteristics and clinical studies

Linezolid is an oxazolidinone indicated in the treatment of nosocomial and community-acquired pneumonia, complicated and uncomplicated skin and skin structure infections and vancomycin-resistant Enterococcus infections. The drug is also approved for use in complicated skin infections and nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus, concurrent bacteremia associated with vancomycin-resistant Enterococcus faecium and concurrent bacteremia associated with community-acquired pneumonia caused by penicillin-susceptible Streptococcus pneumoniae.

Antibiotic resistance: where do ketolides fit?

Burgeoning resistance to antibiotics among common respiratory pathogens poses a very real risk to public health. A need therefore exists for new antibiotics that not only target all common respiratory pathogens, including problematic strains such as penicillin- and macrolide-resistant Streptococcus pneumoniae, but also resist resistance. The ketolides are a new class of antibiotics, of which telithromycin is the first to undergo clinical evaluation, designed to address such issues. These agents possess several innovative structural modifications that not only confer activity against common respiratory pathogens, irrespective of their beta-lactam or macrolide susceptibility, but also minimize the risk of emergent resistance. Ketolides such as telithromycin therefore represent important new options for the empiric treatment of community-acquired respiratory tract infections in an era of increasing resistance. They may be especially useful in areas where macrolide resistance among S. pneumoniae is common because current macrolide treatments against such pathogens are far from optimal.

Pneumococcal conjugate vaccine serotypes of Streptococcus pneumoniae isolates and the antimicrobial susceptibility of such isolates in children with otitis media

The ability of the recently licensed 7-valent pneumococcal conjugate vaccine to cover isolates that cause otitis media, especially drug-resistant ones, was assessed using 500 recently obtained US isolates. Of these isolates, 418 (84%) belonged to vaccine-related serogroups, whereas 82 (16%) belonged to non-vaccine-related serogroups. Serotype 3 accounted for 48 (59%) of the non-vaccine-related serogroups. In addition, 93% of the isolates from patients < or =3 years of age belonged to serotypes that were included in or related to the heptavalent vaccine, compared with 49% of the isolates from older patients (P=.001). Most of the isolates (98%-100%) that were resistant to the antimicrobial agents tested were covered by the heptavalent vaccine, including 95.1% of the isolates from patients <2 years of age. The 7-valent pneumococcal conjugate vaccine could therefore potentially provide protection against all but 1 (type 3) of the common otitis media-associated pneumococcal serogroups identified in this study as well as against 98% of antibiotic-resistant isolates.

Acute exacerbations of chronic bronchitis: what role for the new fluoroquinolones?

Acute exacerbations of chronic bronchitis (AECB) are a major cause of morbidity and mortality. Bacterial pathogens are implicated in about half the episodes of AECB. Empirical antibacterials have a significant benefit in AECB; however, several recent developments have considerably complicated antibacterial choice for this condition. New fluoroquinolone antibacterials introduced in the last decade are theoretically well suited for the treatment of AECB, as the in vitro antimicrobial spectrum of these drugs includes all the major pathogens involved. The pharmacokinetic and pharmacodynamic properties of the new fluoroquinolones are superior to many other antibacterials used to treat AECB. In trials, clinical success with the new fluoroquinolones was equivalent and bacteriological success was occasionally superior to nonfluoroquinolone comparators. However, these clinical trials did not assess several potentially important end-points for which the theoretical superiority of the fluoroquinolones may translate into differences in outcome. Rare but serious adverse effects with some of the new fluoroquinolones have shaken the confidence of prescribing physicians in this class of drugs. Emergence of the resistance of Streptococcus pneumoniae to fluoroquinolones has raised concerns about indiscriminate and widespread use of the new agents for trivial infections. Patients with AECB are a heterogeneous population who should be stratified in order to appropriately choose empirical antibacterial therapy. Highly efficacious antibacterial therapy, such as the new fluoroquinolones, is appropriate as a first-line choice for patients who have risk factors for a poor outcome or are in intensive care units. Such selected use of the new fluoroquinolones balances individual benefit with societal concerns of the use of these agents for AECB.

Pneumococcal resistance: the treatment challenge

OBJECTIVE

To review in vitro and in vivo information dealing with pneumococcal antibiotic resistance and provide a review of the incidence, mechanisms, and controversies surrounding this growing problem. The review is also intended to provide clinicians with relevant recommendations on treatment and prevention of this organism.

DATA SOURCES AND SELECTION

Primary and review articles were identified by MEDLINE search (1966-August 2000) and through secondary resources such as conference proceedings. All of the articles identified from the data sources were evaluated, and all information deemed relevant was included in this review.

DATA SYNTHESIS

The growing incidence and reporting of pneumococcal isolates that are resistant to one or more classes of antibiotics have become a troubling trend that has resulted in significant shifts in treatment. Although clinicians have shifted to a new generation or class of antibiotics when faced with a resistance trend, data with resistant pneumococci show that this may not be necessary. By incorporating the pharmacokinetic and pharmacodynamic data of antimicrobials into the decision-making process, many of the drugs that we have become hesitant to use due to this resistance may still be appropriate if used correctly.

CONCLUSIONS

Appropriate dosing of antimicrobials, combined with optimal use of pneumococcal vaccines, will not only prolong the longevity of some agents, but also hopefully slow resistance development.

Sensibilidade a antimicrobianos de bactérias isoladas do trato respiratório de pacientes com infecções respiratórias adquiridas na comunidade: resultados brasileiros do Programa SENTRY de Vigilância de Resistência a Antimicrobianos dos anos de 1997 e 1998

O tratamento da pneumonia adquirida na comunidade (PAC) é habitualmente empírico e o uso de antimicrobianos é baseado em estudos de vigilância. O programa SENTRY foi desenhado para monitorar a resistência a antimicrobianos através de uma rede internacional de laboratórios. Três centros no Brasil participaram do Programa SENTRY em 1997 e em 1998. Métodos: Um total de 344 isolados bacterianos coletados de pacientes com PAC em 1997 e 1998 foram testados contra mais de 20 agentes antimicrobianos pelo método de microdiluição em caldo. Resultados: Entre os S. pneumoniae (176 isolados), 71,6% foram sensíveis à penicilina. Alto nível de resistência à penicilina e resistência à cefotaxima foram encontrados em 2,3 e 4,0%, respectivamente. As novas quinolonas levofloxacina (MIC90, 2mig/mL) e gatifloxacina (MIC90, 0,5mig/mL) foram ativas contra 100% dos isolados testados. Entre os outros antimicrobianos não beta-lactâmicos testados, os mais ativos foram (% de sensibilidade): cloranfenicol (97,5%) > clindamicina (94%) > azitromicina (90,3%) > claritromicina (89,4%) > tetraciclina (76,4%) > sulfametoxazol/trimetoprim (60,2%). A percentagem de Haemophilus influenzae (101 isolados) resistentes à amoxicilina foi de 90,1%, enquanto entre Moraxella catarrhalis (67 isolados) somente 9,0% foram sensíveis. O ácido clavulânico restaurou a atividade de amoxicilina contra H. influenzae e M. catarrhalis. Porém, H. influenzae demonstrou níveis aumentados de resistência para sulfametoxazol/trimetoprim (55,1% de sensibilidade), claritromicina (80,4% de sensibilidade) e cefaclor (88,2% de sensibilidade). Todos os isolados de H. influenzae e M. catarrhalis foram sensíveis à levofloxacina (MIC90, <= 0,5mig/mL para ambos) e gatifloxacina (MIC90, <= 0,06mig/mL para ambos) apresentando MICs muito baixos. Conclusões: Os resultados indicam que a prevalência de S. pneumoniae com alto grau de resistência à penicilina é ainda baixa no Brasil; porém, a prevalência de S. pneumoniae com resistência intermediária à penicilina e resistência cruzada a outras classes de antimicrobianos é relativamente alta em nosso meio. Por outro lado, as novas quinolonas são altamente ativas contra S. pneumoniae e outros patógenos responsáveis por infecções respiratórias adquiridas na comunidade.

Impact of Antimicrobial Resistance on the Treatment of Invasive Pneumococcal Infections

Infectious diseases, such as pneumococcal pneumonia, which were almost invariably lethal in the pre-antibiotic era, caused radically less mortality with the advent of antimicrobial chemotherapy. However, the use, misuse, and abuse of these agents have led to the emergence of antimicrobial resistance. In the past, pneumococci were all exquisitely sensitive to penicillin G. By the late 1960s, penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) was being described. Since then, this problem has achieved epidemic proportions in many areas of the world, including the United States. Many experts no longer consider penicillin an acceptable therapy for patients suspected of having invasive pneumococcal disease, especially if the central nervous system (CNS) is involved. Recommendations for therapy are based on theoretical concerns, in vitro susceptibility testing, animal data, and a few, scattered reports of penicillin failure in patients with invasive disease.

Emerging therapies for serious gram-positive bacterial infections: a focus on linezolid

Respiratory tract infections and skin and soft-tissue infections frequently are caused by gram-positive cocci, and treating these infections with standard antibiotics has recently become problematic. Many of the primary pathogens causing these infections are now resistant to current standard treatment regimens. In addition, the frequency of these infections is increasing, particularly among patients with complex medical conditions. Thus, new and effective antimicrobial agents are needed, and many are currently in various stages of development. Linezolid, the first approved oxazolidinone, has enhanced activity against gram-positive organisms. Recent results of 5 large, randomized, phase 3 trials evaluating linezolid for the treatment of community-acquired pneumonia, nosocomial pneumonia, and uncomplicated and complicated skin and soft-tissue infections are encouraging and indicate that linezolid is as effective as standard comparator agents as therapy for these infections. Thus, the recent availability of linezolid offers clinicians a promising new agent for the treatment of serious gram-positive bacterial infections.

New Fluoroquinolones: Real and Potential Roles

The second-generation fluoroquinolones have enjoyed successful clinical use for more than 10 years in many countries, and they have a valued and proven record of safety and efficacy. However, deficiencies with respect to gram-positive and anaerobic organisms limit the use of these agents in respiratory, intra-abdominal, and pelvic infections. New, third-generation agents with dramatically increased activity against gram-positive and anaerobic bacteria--notably, Streptococcus pneumoniae and Bacteroides fragilis--have shown high rates of efficacy in pneumonia, bronchitis, and surgical and gynecologic infections. Although most of these new drugs produce similar clinical results, adverse reaction profiles differ and may influence therapeutic choices.